问如何在自定义布局集合视图中取消选择不可见的单元格？

EN

let prevCell = try collectionView.cellForItem(at: previouslySelectedIndex) as? MyCollectionViewController.MyContentCell 

let cell = self.collectionView?.dataSource?.collectionView(self.collectionView!, cellForItemAt: IndexPath(row: 0, section: 0))

func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
        if(collectionView == customContentCollectionView){
            let cell:MyContentCell = collectionView.cellForItem(at: indexPath)! as! MyCollectionViewController.MyContentCell

            // DESELECTION CODE
            if(previouslySelectedIndex != nil){
                // following line is error prone (executes but may or may not fetch the cell, sometimes deselect sometimes doesnt)
                if let prevCell = try collectionView.cellForItem(at: previouslySelectedIndex) as? MyCollectionViewController.MyContentCell {

                    // Also tried with this following (executes but fails sometimes, in case not fetching the cell)
                    //let prevCell = try collectionView.cellForItem(at: previouslySelectedIndex)! as! MyCollectionViewController.MyContentCell

                    // Tried this one as well, fetching the previously selected cell using datasource, not directly from collection view
                    // let prevCell = customContentCollectionView.dataSource?.collectionView(collectionView, cellForItemAt: previouslySelectedIndex) as? MyCollectionViewController.MyContentCell

                    prevCell?.shapeLayer.strokeColor = bubbleBorder.cgColor
                    prevCell?.shapeLayer.fillColor = bubbleFill.cgColor
                    prevCell?.shapeLayer.shadowOpacity = 0.0
                    prevCell?.labelCount.textColor = bubbleBorder
                }
            }

            // SELECTION CODE HERE GOES PRETTY WELL
                previouslySelectedIndex = indexPath
        }
    }

override func prepareForReuse() {
    //reset all the fields of cell
    self.shapeLayer.strokeColor = bubbleBorder.cgColor
    self.shapeLayer.fillColor = bubbleFill.cgColor
    self.shapeLayer.shadowOpacity = 0.0
    self.labelCount.textColor = bubbleBorder
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
     //your code to create cell n all

     if(indexPath == previouslySelectedIndex) {
         //your code to select the cell
     }

     return cell
 }